Personal computing devices, such as mobile telephones (e.g., feature phones and smart phones), personal digital assistants (PDA), and mobile computers (e.g., tablet, netbook, and notebook computers), have become prevalent in people's daily lives. Many such devices are capable of supporting a variety of functionalities. Often, people carry relatively small and yet highly versatile mobile devices with them as they go through their daily lives (e.g., visit different places, participate in different events, perform different activities, etc.), and these mobile devices become extremely useful tools that bring convenience and flexibility to people's lives.